1. Field of the Invention
The present invention relates to an exhaust gas purifying apparatus, which includes a collector that collects particles in exhaust gas (exhaust particles) of an internal combustion engine. Also, the present invention relates to an estimating method for estimating a collected amount of the exhaust particles collected by the collector.
2. Description of Related Art
Recently, in a diesel internal combustion engine mounted on a vehicle, a collector that collects exhaust particles is provided in a middle of an exhaust pipe in order to reduce the exhaust particles in exhaust gas.
The collector is generally a ceramic porous media that includes multiple exhaust gas passages. The collector adsorbs and collects the exhaust particles when the exhaust gas passes through porous partitions that define the exhaust gas passages. When the collected exhaust particles that are collected by the collector remain in the collector, a pressure loss is increased so that an efficiency of the engine will be degraded. Thus, the collector needs to be regenerated by burning (oxidizing) the exhaust particles in the collector when a computed value of a collected amount reaches a predetermined value.
Specifically, the collector carries an oxidation catalytic converter. At a time of the regeneration of the collector, after a main inaction, a post injection is made to supply a hydrocarbon (HC) into the collector such that an interior of the collector is heated due to a catalytic reaction of the HC and the exhaust particles collected in the collector are burned and removed.
An estimation method for estimating the collected amount of the exhaust particles collected in the collector based on a pressure difference across the collector and a flow rate of the exhaust gas is known (see Japanese Unexamined Patent Publication No. 2004-19523, corresponding to U.S. Pat. No. 6,829,889). Also, another method is disclosed to estimate the collected amount based on a temperature of the exhaust gas. This is because physical properties (e.g., viscosity, density) of the exhaust gas changes depending on the temperature of the exhaust gas that passes through the collector.
However, in an apparatus disclosed in Japanese Unexamined Patent Publication No. 2004-19523, a change of physical properties of the exhaust gas, due to a change of exhaust gas components, is not considered. Thus, the may lead to an erroneous estimated value (deviation) of the collected amount.